Leo Demidov, the main character of the fictional thrillers by Tom Rob Smith, was born in the Soviet Union under the reign of Stalin. As a young boy his father left under the guise of trying to find food and a better life for his wife and two sons. Left to fend on their own, Leo (then called Pavel) helped his mother, Oksana, and younger brother Andrei to survive the harsh winters. Over the course of Child 44 it is learned how Pavel becomes Leo and is raised by Stepan and Anna.

Leo is hailed as a hero due to his actions and a lucky photo taken during a conflict in which he helped to overthrow enemy tanks. He joins the MGB, an elite faction of the military tasked with identifying, questioning and sentencing traitors and enemies of the state.

Raisa, Leo’s wife has no family of her own, as they were all killed during a bombing of her hometown by her own country to ensure that the Germans were unable to find anything of value in the town. Raisa was injured during a war time conflict and can not conceive children. This, along with circumstances described in Child 44, leads Leo and Raisa to adopt two young girls, Zoya and Elena, who become primary characters in The Secret Speech.